BYZANTINE ARCHITECTURE 31 form of capital in the later churches, and must have been in continuous use from the earliest date. It occurs in S. John of the Studion, the Diaconissa, the Chora3 and in many other churches. Here the classic form is accurately adhered to, but, as the curved abacus was unsuitable to the arch, a large splayed abacus or impost block is placed above the capital. It is a general feature of the Byzantine capital that it projects at no point beyond the impost line of the arch, thus' differing both from the classic and the Gothic forms. VII. The Windblown Acanthus.—This is found in the churches of Salonica and Ravenna. Three examples are mentioned as seen in Constantinople, two near the Diaconissa, forming bases for the posts of a wooden porch to a house ; one is the cistern commonly known as the cistern of Pulcheria. Window Capitals.—In shafted window of several lights, the impost piers between the arches are of the full thickness of the wall, but are very narrow from side to side. Similarly the shafts are almost slabs placed across the wall, and sometimes, as in the Pammakaristos, are carved on their narrow faces. The capitals are cubical, of slight projection at the sides, but spreading widely at the ends, while the bases closely resemble capitals turned upside down. As with columns, the joints at base and necking are bedded in sheet lead. Floors.—The floors are usually of thick red brick tiles, some .31 cm. square, or, as in S. Theodore, hexagonal, .34 cm. across by 45 cm. from point to point. Marble floors were used when possible, inlaid with patterns, or in slabs surrounded by borders of coloured marbles, as is still seen in a portion of the floor in the Pantokrator (Fig. 76). Decoration.—Of the churches of Constantinople only S. Sophia, S. Mary Diaconissa, the South Church of the Pantokrator, and the Chora, retain any considerable part of their original decoration. The first is beyond our present scope, but from the general tone and atmosphere which still linger there we are able to appreciate the effect of the same style of decoration where it survives in less complete form.